1. Technical Field of the Invention
The present invention relates to an optical laminate.
2. Description of the Related Art
Liquid crystal cells generally used in liquid crystal displays such as a TN liquid crystal cell (TFT), a STN liquid crystal cell (STN) and the like, have a structure in which a liquid crystal component is sandwiched between two glass base materials. On the surface of the glass base material, an optical film such as a polarizing film, phase retardation film and the like is laminated via an adhesive composed mainly of an acrylic resin.
An optical laminate composed of an anti-reflection film 1, polarizing film 2, adhesive layer 3, glass cell for liquid crystal display 4, adhesive layer 5 and polarizing film 6 laminated in this order is in general used.
Adhesive layers 3 and 5 used in such an optical laminate tend to generate curl and the like due to large dimension change by expansion and shrinkage under heating or moistening and heating conditions, consequently, there are problems such as occurrence of foaming in an adhesive layer of the resulted optical laminate, generation of peeling between an adhesive layer and a glass base material, and the like. Under heating or moistening and heating conditions, distribution of remaining stress acting on an optical film such as an anti-reflection film 1, polarizing film 2 and the like becomes non-uniform, concentration of stress occurs around peripheral parts of an optical laminate, consequently, there is a problem that light leakage occurs in a TN liquid crystal cell (TFT).
Further, recently, such a liquid display is used for vehicle-mounted applications such as a car navigation system and the like, however, in vehicle-mounted applications, durability such as no occurrence of appearance change such as foaming, floating, peeling, fogging and the like is also being required.
To solve such problems, there is a suggestion on an adhesive essentially consisting of an acrylic resin composition composed of a high molecular weight acrylic resin having a weight-average molecular weight of 900,000 to 2,500,000, a Tg of −45° C. or lower and a SP value of 8.7 to 9.3 and a low molecular weight acrylic resin having a weight-average molecular weight of 50000 to 200000, a Tg of −40 to 0° C. and a SP value of 8.7 to 9.3 (Japanese Patent Application Laid-Open (JP-A) No. 2004-2782 [claim 1], [0129]).
However, when an optical laminate having a constitution of anti-reflection film/polarizing film/adhesive layer/glass base material/adhesive layer/polarizing film is produced using the adhesive on both surfaces of the glass base material and one cycle of 60° C.→−20° C.→60° C. is repeated 100 times, then, peeling, hazing and the like occur on the surface of a glass plate, durability thereof is not sufficient, and light leakage occurs, in some case.